Integrated circuits, such as microprocessors and memory devices, include many metal-oxide-semiconductor field-effect transistors (MOSFETs), which provide the basic switching functions to implement logic gates, data storage, power switching, and the like. When MOSFETs are connected in parallel as shown in FIG. 1A to handle large current in slow switching applications, parameter mismatch (e.g., on resistance, threshold voltage, channel lengths) between MOSFETs results in dynamic current imbalance, and thus causing current hogging. Current hogging takes places when a larger fraction of a current passes through one of several parallel MOSFETs due to lower threshold voltage or channel length. Since that particular MOSFET dissipates most of the device power, localized hot spots appear. The higher temperature further lowers threshold voltage of that MOSFET and draws more power. Ultimately, thermal runaway would occur.
It is known in the field that source ballasting may provide negative feedback to counter current hogging. Thus, in order to avoid current hogging, a source ballast resistor is typically added in series with each MOSFET as shown in FIG. 1B to equalize the distribution of the load current among the parallel MOSFETs. It is within this context that embodiments of the present invention arise.